This invention pertains to hermetically sealed, positive displacement compressors for compressing refrigerant in refrigeration systems such as air conditioners, refrigerators and the like. In particular, the invention relates to multi-unit compressor assemblies wherein a plurality of compressor mechanisms are housed in a common hermetic housing or shell. More particularly, the invention describes two rotary compressor mechanisms of the type which may be oriented horizontally or vertically, a common electric motor centrally disposed between each of the compressor mechanisms driving their roller pistons in an orbital fashion around the cylindrical walls of their compression chambers, a spring biased vane abutting the outside surface of the roller piston and reciprocating in a slot provided in the cylinder block as the roller piston orbits.
Twin rotary compressors are well known in the art, as exemplified by U.S. Pat. No. 4,889,475 which is assigned to assignee of the present application. The entire interior surface of the housings of previous twin rotary compressor assemblies have generally been subjected to either suction or discharge pressure. For example, suction pressure may be provided directly via tubes to each of the twin rotary compressor mechanisms in a compressor assembly, with each of the compressor mechanisms discharging discharge pressure gas to the interior of the compressor housing, from which it flows from the compressor assembly to the condenser of a refrigeration system. The disadvantage associated with this configuration is that the electric motor assembly is subjected to high temperature discharge gases, which undermines its operating efficiency. It is thus desirable to maintain the motor at temperatures associated more with suction pressure gases.
Alternatively, the housings of previous compressor assemblies are provided with suction pressure gas from the evaporator core of a refrigerant system, which then flows into the suction ports of each of the rotary compressor mechanisms, each compressor mechanism individually discharging via tubes its discharge pressure gases from the compressor assembly housing, outside of which they are combined and supplied to the condenser. A disadvantage associated with this configuration is that the discharge gases flow directly from the compression chambers to the outside of the compressor housing, often requiring a costly external muffler or mufflers to quiet fluid-borne noise prior to the refrigerant being provided to the condenser. A compressor which requires no separate, external muffling, avoiding the packaging requirements and costs associated therewith, is greatly desired.
Further, previous rotary compressors are provided with discharge ports in the surfaces of either the main or outboard bearing enclosing the cylindrical compression chamber. The port having a direction of flow in the axial direction of the compression chamber, perpendicular to the plane of roller piston revolution. As the roller piston revolves epicyclically about the cylindrical wall of the compression chamber, one of its axial outer surfaces sweeps past the discharge port, partly covering it before the end of the compression cycle, reducing the area available for discharge gases to exit the compression chamber. It is desirable to provide a uniform discharge port area throughout the compression cycle to ensure that the compressed gases may flow freely and be fully exhausted from the compression chamber.
In previous rotary compressors, once the roller piston rolls past the discharge port opening, previously exhausted discharge pressure level gases are free to expand back into the compression chamber, which is then currently at a substantially lower pressure. The gases which re-enter the compression chamber through the discharge port are recompressed and again exhausted therefrom, contributing to compressor inefficiency. A means of preventing the reentry of previously discharged gases into the compression chamber through the discharge port is highly desired.
Sound waves associated with discharge pressure pulses, as well as mechanical noises associated with the operation of the compressor mechanisms, are readily transmitted by discharge pressure gases, the molecules of which are densely packed. These sound waves may impinge upon the compressor housing itself, generating noise which may be objectionable in the space in which the compressor assembly itself is located. Therefore, it is desirable to muffle such noises immediately after the compression cycle and before the gases reach the interior surface of the compressor housing, without adding significant cost to the compressor assembly.
Finally, twin rotary compressor heretofore understood, provided beneficial mechanical vibrational qualities, due to symmetrical and 180 degree offset compressor mechanism strokes, however, improvement in routing the gas through the compressor to decrease fluid-borne noise has been a desirous, yet unsatisfied need.